Research: What causes the growth of toxic algae in the waters of the Kinneret and the threat to water quality in Israel

Toxic blue-green algae invade freshwater bodies and enslave other organisms

A new study at the Hebrew University has discovered for the first time a major factor in the development of toxic blue algae in freshwater bodies. The growing phenomenon of the appearance of these toxic organisms causes concern in many parts of the world because of their harmful effect on the quality of drinking water, and their ability to cause death among humans and animals. The new research of Yonatan Bar-Yosef from the Hebrew University could be of great value to water authorities seeking to control the penetration of blue algae into fresh water sources.

The toxic algae were observed in the Sea of ​​Galilee for the first time in 1994 and continued to be discovered during every summer in the following years. The conditions that led to their bloom and other toxic compounds in freshwater bodies were unknown until now, but research at the Hebrew University sheds new light on the phenomenon.

The research of Yonatan Bar-Yosef, a doctoral student in Prof. Aharon Kaplan's research group at the Silverman Institute of Life Sciences at the Hebrew University, in collaboration with Dr. Assaf Suknik and Dr. Ora Hadas from the Kinneret Laboratory, offers an innovative mechanism for increasing the prevalence and success of these blue algae - Competition between them and other organisms in water.

The study indicates a new phenomenon of "enslavement" in water. The blue algae are known to secrete the toxin Cylindrospermopsin into drinking water. It was found that the toxin secreted by the blue algae induces conditions of phosphorus deficiency in other organisms - even in the presence of sufficient phosphorus available in the environment. The simulated deficiency causes these organisms to secrete a large amount of an enzyme that releases phosphorus from organic compounds found in the water, thereby increasing its availability, and this in an attempt to absorb the phosphorus that serves as their main food.

A high absorption capacity of the phosphorus in the blue algae allows them to successfully compete for the released phosphorus against the other organisms. Their successful use of the toxin at the same time as the utilization of the other organisms gives them an advantage over their competitors and explains their success in conditions of lack of nutrients.

For the blue algae, the production of the toxin and its secretion are significantly "cheaper" than the production of the enzyme and its secretion to release phosphorus. These findings also explain the original biological role of the toxin and open new ways to treat the problem.

Prof. Aharon Kaplan points out that in the last decade there has been an increase in blooms of toxic blue algae in lakes and freshwater reservoirs all over the world, and in Lake Kinneret in particular, even though the administrations responsible for managing these bodies of water are putting considerable effort into reducing the amount of nutrients, especially phosphorus, coming from the water collection areas to the lakes. "These blooms have serious consequences for the quality of the water and our ability to use it for drinking or other uses," says Prof. Kaplan. "Toxins produced by various cyanobacteria have already caused many deaths of humans and animals, are known to promote cancerous tumors and damage the liver."

The study was published on August 12, 2010 in the prestigious journal Current Biology.